Loud speaker



A. ARMER LOUD SPEAKER Oct. 17, 1933.

Filed Sept. 2. 1930 2 Sheets-Sheet l INVENTOR.

Agr/N A. ARMER LOUD SPEAKER Oct. 17, 1933.

Filed Sept. 2, 1950 2 Sheets-Sheet 2 IN VEN TOR. #usr/1V xP/WEI? Patented Oct. 17, 1933 LOUD SPEAKER Austin Armer, Berkeley, Calif., assignor to The Magnavox Company, Oakland, Calif., a corporation of Arizona Application September 2, 1230. Serial No. 479,153

8 Claims.

My present invention relates to sound repro1 ducers and more particularly to a device of this character for the reproduction of radio signals and phonographic sound recordings.

An object of my invention is to provide a new and novel type of actuating element for loud speakers and pick-ups of the electromagnetic type which is simple in construction and eicient in operation. i

A further object of my invention is to provide a simple form of diaphragm actuating element for loud speakers which will in addition to driving the diaphragm serve as a support for .the apex of a conical diaphragm and also function as the secondary of an input transformer.

Another object of my invention is to provide a combined transformer and actuating element assembly for loud speakers and pick-ups in which a single element forms both the actuating element and the primary or secondary of a transformer. l

A further object of my invention is to provide a moving element for loud speakers and pick-ups of the electromagnetic type in which a maximum of conductivity per unit of mass in the moving system is obtained.

Other objects and advantages of my invention will be in part evident to those skilled in the art and in part pointed out in detail in the following description.

In the accompanying drawings, I have shown by Way of illustration and not of limitation preferred embodiments of the invention. In these drawings wherein like numerals refer to like parts throughout the several Views- Fig. 1 is a side elevation in section showing one embodiment of my invention,

' Fig. 2 is a rear View in elevation of the speaker shown in Fig. 1,

Fig. 3 is a perspective view showing one form4 Fig. 7 is a perspective view of the diaphragm actuating element illustrated in Fig. 5,

Fig. 8 is a schematic diagram showing the system of connection,

Fig. 9 is a side elevation showing my invention embodied in a phonographic pick-up device, and

Y Fig. 10 is a plan View of the device shown in j Fig. 9.

In Fig. 1, 10 designates a cone housing or supporting member in which there is mounted a conical diaphragmV 1l, the diaphragm l1 being movably mounted upon the housing 10 by means f' i This j air-gap 18 is formed. In mounting the iield structure i4`upon the housing 10 it will be noted that only the pole piece 16 engages the housing 10 and that the pole piece 17 is suspended freely out of Contact with other metallic parts. The housing l0 is mountedupon a base member 19 which also carries a suitable transformer core 20. Surrounding the transformer core 20 there is shown a-primary winding 21 which is adapted to connect with the modulated current output of a radio amplier or other source of sound producing current. Attached to the rapex of the cone 11 and disposed within the air-gap 18, I show my improved diaphragm actuating element 22. This element as here illustrated is mounted upon the housing 10 at the point 23 so that its upper end may flex freely under the influence of magnetic forces generated Within the air-gap 18 to actuate the cone 11. The lower half of the member 22 is shown as vturned at right angles to the upper half and as disposed about the central leg of the transformer cone 20. A terminal board 24 is also provided upon the base 19 upon which the various external connections to the speaker are made.

By referring to Figs. 2 and 3 it will be seen that the lower portion of the diaphragm actuating member 22 is so formed that it will be of relatively low resistance. To accomplish this feature `I show the turn 'forming portion of the member 22 as provided with flanged sides 25 at the point where the member passes through the core 20. It will also be 'noted that the upper half of the element 22 is of a reduced cross section and as a result yields a maximum current density in that portion of the' conductor subjected tothe reaction of the magnetic flux in the air-gap, By referring particularly to Fig. 3 it will be noted that the upper half of the element 22 comprises outwardly diverging legs 26 which terminate in a horizontally disposed portion 2'7. Formed upon the portion 27 there is a suitable boss 28 by means of which the element 22 is attached to the cone 11. In the drawings this attachment is effected by means of a small bolt 29.

In order to ensure a proper spacing of the pole pieces 16 and 17, I provide a bridgev member 29 as shown in Fig. 4. This bridge member comprises two strips of a nonmagnetic material rmly secured to the pole pieces near the ends of the air-gap 18.

In Figs. 5 and 6 which show a more simplied form of my invention the electromagnetic neld structure i4 is mounted upon a support 30 turned out from the base 19 and the cone housing 10 as supported upon two upwardly projecting arms 31 carried by the base 19. The transformer core 2i) is here shown as disposed horizontally so that the cone actuating element, designated Yby the numeral 32, and constructed of a single piece oi" metal may be disposed in substantially one plane.

The cone actuating element 32 like the element 22 is formed of a single piece of metal without joints so that a complete electric circuit is formed which passes in inductive relation with the magnetic transformer eld and in operative relation with the constant current magnetic held. In forming the elements 22 and 32, I prefer to use aluminum or a similar light metal of high current conductivity. In this latter 4embodiment it will be noted that the element 32 is of simple vform and consequently will be easier to stamp out than would the element illustrated in Figs. 1, 2 and 3 of the drawings. As a further modification, for the-purpose of cutting down the generation of eddy currents, I may provide relatively narrow slits 33 in the moving conductor portion 27.

When'my invention is embodied in a phonographic pick-up device I utilize substantially similar parts throughout except that I substitute a record stylus or needle 41 for the diaphragm 11. A simple arrangement is illustrated in Figs. 9 and 10 wherein I show an actuating element 42 disposed on edge with respectto a phonograph record 43.

As here shown, the stylus 41 is secured to the end of the conductor portion of the actuating element 42 and is disposed in alignment therewith so that as the needle or stylus 41 follows the record groove the conductor will be flexed about supporting screws 44 and between the poles 45 and 46 of the electromagnet coil 47. Arranged in back of the supporting screw I show a transformer core 48 upon which a suitable secondary winding 49 is disposed in inductive relation with the turn vforming portion of the actuating element 42.

For a description of the operation of my improved speaker reference should be had to Fig.

' 8 wherein I have shown schematically a mag-y netic iield structure 34 having an air-gap 35 which is energized by an electromagnet coil 36. In this embodiment the conductor portion of the element 22 is shown as disposed in an airgap formed between poles 37 and 38 and attached directly to the conical diaphragm 11. The trans-,

former core 20 is disposed vertically and the primary winding 21 isprovided with suitable terminals 39 and 40. When the speaker is in operation the eld coil 36 will be energized from a suitable source of direct current such, for instance, as a battery or rectifier of the type usually provided with modern radio sets.

When the output of a radio set or phonographic reproducer is impressed across the primary coil 21 of the transformer a magnetic flux will be set up in the core 20 which will cause a corresponding modulated current to be induced into the element 22 and this current under the influence oi the flux between the poles 37 and 38 will cause the conductor portion 27 of the element 22 to move back and forth in response tothe currents impressed upon the primary coil 21 and thus cause the diaphragm 11 to reproduce sound waves corresponding thereto.

When producing currents from sound recording the stylus 4l will be caused to move between the poles 45 and 46 by the record groove and as a result of this movement in the magnetic iield currents will be generated in the conductor portion which will ow through the turn forming portion. These currents will vary in magnitude and direction and will cause a varying iiux to cut the secondary winding 49 and set up a voltage therein which when passed through a suitable amplier or connected directly to a sound Areproducing device will actuate the latter toreproduce the record. While I have, for the sake of clearness and in order to disclose my invention so that the same can be readily understood, described land illus` trated specific devices and arrangements, I desire to have it understood that this invention is not limited to the specific means disclosed .but

may be embodied in other ways that will suggest themselves, in view of this broad disclosure, to

persons skilled in the art. It is believed that this invention is broadly new and it is desired vto claim it as such so that all such changes -as come within the scope of the appended claims are to be considered as part of this invention. Having thus described my invention, what I claim and desire to secure by Letters Patent is 1. In a loud speaker of thel electrodynamic type, the combination of a magnetic eld struc-,.

transformer core, a single jointless secondary.,

conductor forming a closed electrical circuit disposed in inductive relation with said primary winding and having a flexible portion thereof extending into the air gap between said magnetic poles, and means formed integrally upon said-,.

conductor for engaging a sound reproducing diaphragm.

2. In sound reproducing apparatus of the electrodynamic type, the combination of a magnetic field structure having oppositely disposed mag-u netic poles spaced to form a straight magnetic air gap, a transformer core mounted in fixed relation at one side of said air gap, a winding upon said transformer core, a single jointless conductor forming a closed circuit disposed in inductive, relation with said Winding and having a flexible` portion thereof extending into the air gap between said magnetic poles, and means carried by said iiexible portion for rendering it operative to reproduce sound.

3. In sound reproducingapparatus, thel com-C bination of a magnetic eld structure having a pair of magnetic poles between which there is formed a magnetic air gap, a transformercore iso mounted in in nxed relation with respect to said air gap, a winding upon said transformer core,` and a one piece jointless conductor mounted in inductive relation with said winding and having portions extending outwardly in the same plane thereof, said conductor having another portion,

turned out in a different plane adjacent said air iso gap and disposed therein adapted to actuate a sound reproducing diaphragm. y

4. An actuating element for loud speakers and pick-ups of the electrodynamic type, comprising a jointless piece of metal forming a closed electrical circuit having a single relatively straight portion adapted to be disposed in a magnetic field and a transformer turn forming portion adapted to be disposed in inductive relation with a transformer winding, and a fixed support for said element located between said portions, whereby the straight portion may move in said magnetic field by flexing said piece of metal adjacent said support.

5. An actuating conductor for speakers and pick-ups of the electrodynamic type, comprising a jointless element cut from a single sheet of metal to form a continuous electric circuit having a straight armature conductor portion adapted to be disposed in a magnetic eld and another portion extending from the ends thereof in a plane at right angles thereto which forms a winding of a transformer.

6. In a loud speaker of the electrodynamic type, the combination of a constant magnetic field having an air-gap therein, a transformer core magnetically independent of said magnetic field, a single continuous and jointless conductor having a straight portion disposed in said air-gap and a anged portion disposed upon said transformer core, a transformer primary winding upon said core, and a sound producing diaphragm connected to said conductor, whereby said diaphragm will be actuated in response to the current impressed upon said transformer primary winding.

7. In a sound reproducing device of the electrodynamic type, the combination of a magnetic neld having an air-gap, a shell type transformer core having a winding thereupon disposed in spaced relation with said air-gap, a. second winding upon said transformer core formed of sheet metal having a projecting portion disposed in said air-gap, and flanges upon the portion of said second Winding on the transformer core which extend between the legs of the core and increase the conductance of this latter portion of the second winding. f

8. In a sound reporducing `device of the electrodynamic type, the combination of a magnetic field having an air-gap, a transformer core disposed in spaced relation with said air-gap, and a conductorforming a closed circuit upon said transformer core having a flexible portion disposed in said air-gap and a at portion having flanges disposed upon said transformer core, said anges being adapted to stiften this portion of the conductor and increase its conductivity.

AUSTIN ARMER. 

